The experiments described in this proposal are aimed at extending our knowledge of eucaryotic gene structure and function. We will elucidate the molecular biology of the gene which codes for the enzyme glycerol-3-phosphate dehydrogenase from Drosophila. This enzyme is found in different tissues at very different specific activities. A contribution to our understanding of the differentiated state will be to provide a molecular basis for this difference. We will compare enzyme turnover in larval fat body and adult flight muscle. We will also compare the structure, turnover and rates of synthesis of GPDH mRNA in these tissues. Through production of purified GPDH mRNA and its cDNA we will be able to analyze the molecular structure of the GPDH locus and in the future make correlations with formal genetic structural analysis. We should also be able to compare the evolutionary rates of divergence of the coding sequence with any intervening sequences and sequences neighboring GPDH coding sequences in the genomic DNA.